Degradation control of display pixels for a high definition display

ABSTRACT

An apparatus includes a display and an image processing system. The display has an array of horizontal pixels and vertical pixels. The image processing system is configured to present an image on the display as a visible display array having a smaller size than the array and to shift the visible display array by at least one pixel.

BACKGROUND

Field

The present disclosure relates generally to self-emitting highdefinition (HD) displays, and more particularly, to pixel control of thedisplays.

Background

High definition (HD) displays are used in a variety of applications,including televisions, personal computers and tablets, smart phones, andcamera viewfinders. Some forms of HD display technology include liquidcrystal display (LCD), plasma, light emitting diode (LED) and organicLED (OLED). The HD display screen is formed by an array of pixels, whereeach pixel typically includes three color elements, blue, green, andred. Backlit displays, such as LCD, experience a homogenous degradationin luminance with progression of service duty. In self-emittingdisplays, such as plasma, LED, and OLED, a degradation in pixel outputis known to occur as the pixels are energized over time and the variouscolor elements accumulate a service duty. The pixel degradation forself-emitting displays is thus manifested by a drop in luminance for theparticular color element. Consequently, certain colors of theself-emitting display may become noticeably dimmer over time. Moreover,the blue, green and red elements do not degrade at an even rate,resulting in a color shift away from the weaker color. For example, theblue elements may degrade at a faster rate, resulting in the displayhaving weaker blue hues, and more prominent red and green overall.

Pixel degradation can be accelerated when an overlay is consistentlypresent on the display. Take for instance a cross hair indicatordigitally superimposed on a camera viewfinder to assist the user incentering a subject for video capture. Should the overlay remain in afixed position for an extended period and remain the same color, itfollows that the pixels energized to form the overlay will experience anaccelerated degradation for the particular color element employed.

SUMMARY

In an aspect of the disclosure, an apparatus for shifting a video imageacross a display by one or more pixels horizontally and vertically isprovided, thus extending the lifetime of pixels used to display a fixedoverlay and retarding the degradation of the pixels.

In another aspect of the disclosure, an apparatus includes a displayhaving an array of horizontal pixels and vertical pixels and an imageprocessing system configured to present an image on the display as avisible display array having a smaller size than the array; and to shiftthe visible display array by at least one pixel.

In another aspect of the disclosure, a camera includes an imagerconfigured to convert photons to an electrical image signal; and aviewfinder including a display having an array of horizontal pixels andvertical pixels; and an image processing system configured to present animage on the display based on the electrical image signal as a visibledisplay array having a smaller size than the array; and to shift thevisible display array by at least one pixel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a display having a reduced visualdisplay region of pixels to accommodate pixel array shifting.

FIG. 2 is a flow chart of an example method for scaling and shifting thepixel array of visual display region.

FIG. 3 shows diagram of an exemplary apparatus for scaling and shiftingthe pixel array on a display.

FIG. 4 is a diagram illustrating an exemplary hardware implementationfor a display apparatus configured to perform scaling and shifting of apixel array.

FIG. 5 is a block diagram illustrating an exemplary camera system havinga viewfinder configured to perform scaling and shifting of a pixelarray.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Certain aspects of video production systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawing by various blocks, modules, components,circuits, steps, processes, algorithms, etc. (collectively referred toas “elements”). These elements may be implemented using electronichardware, computer software, or any combination thereof. Whether suchelements are implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented with an “image processingsystem” that includes one or more processors. Examples of processorsinclude microprocessors, microcontrollers, digital signal processors(DSPs), field programmable gate arrays (FPGAs), programmable logicdevices (PLDs), state machines, gated logic, discrete hardware circuits,and other suitable hardware configured to perform the variousfunctionalities described throughout this disclosure. The imageprocessing system may also be implemented on a processing device thatincludes any one or more of the above processors. One or more processorsin the image processing system may execute software. Software shall beconstrued broadly to mean instructions, instruction sets, code, codesegments, program code, programs, subprograms, software modules,applications, software applications, software packages, routines,subroutines, objects, executables, threads of execution, procedures,functions, etc., whether referred to as software, firmware, middleware,microcode, hardware description language, or otherwise. The software mayreside on a non-transitory computer-readable medium. A computer-readablemedium may include, by way of example, non-transitory storage such as amagnetic storage device (e.g., hard disk, floppy disk, magnetic strip),an optical disk (e.g., compact disk (CD), digital versatile disk (DVD)),a smart card, a flash memory device (e.g., card, stick, key drive),random access memory (RAM), read only memory (ROM), programmable ROM(PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), aregister, a removable disk, as well as a carrier wave, a transmissionline, and any other suitable medium for storing or transmittingsoftware. The computer-readable medium may be resident in the imageprocessing system, external to the image processing system, ordistributed across multiple entities including the image processingsystem. Those skilled in the art will recognize how best to implementthe described functionality presented throughout this disclosuredepending on the particular application and the overall designconstraints imposed on the overall system.

Certain embodiments of the described invention provide an adaptableviewfinder that may be used to display video images having a broad rangeof formats and/or resolutions. A pixel control means may be providedwithin the viewfinder for retarding pixel degradation caused by fixedoverlays. A pixel control means may be provided within the viewfinderfor compensation of pixel degradation caused by fixed overlays.

FIG. 1 illustrates a video display arrangement 100 that has a full fieldof pixels 102, such as 1920 horizontal lines and 1080 vertical lines ofpixels, for example. In this aspect, a visible field 104 is defined thatis smaller than the full field 102, reduced according to (1920-n)horizontal lines and (1080-m) vertical lines of pixels, where n≧1 andm≧1. As shown in FIG. 1, reserved horizontal regions 106 and 107 areeach n/2 pixels wide, and reserved vertical regions 108 and 109 are eachm/2 pixels long. Alternatively, visible field 104 may be positioned suchthat a reserved horizontal region 106 of n pixels exists, and region 107is 0 pixels wide, or vice-versa. In another alternative example, thereserved vertical region 108 may be m pixels wide, while reservedvertical region 109 is 0 pixels wide. In another alternative example,the visible field 104 may be positioned such that an asymmetrical numberof pixels exist in regions 106 and 107, and/or in regions 108 and 109.The pixels within the reserved regions 106-109 may be in a de-energizedstandby state. An example overlay 110 is shown, which may be used as acentered cross mark for guiding the camera user to the center of viewduring recording. Other indicators may be overlaid in the field eitherin the alternative or in combination with the overlay 110 as shown. Inthis aspect, the visual field 104 may be shifted horizontally by Npixels for the range (1≦N≦n) and/or shifted vertically by M pixels forthe range (1≦M≦m), which then activates the reserved pixels previouslyin a standby state, as needed. For example, a shift of the visible field104 into the reserved horizontal region 106 for N=1 pixel will triggerthe first adjacent pixel in each horizontal row along the reservedregion 106 to display the shifted image. Meanwhile, the first adjacentpixel in each horizontal row of buffer region 107 may become inactiveand placed in a standby state until a subsequent shift of the visiblefield 104 returns back to within the reserved region 107. In a similarmanner, the visible field 104 may be shifted vertically, using thereserved regions 108 and 109. As the pixel field 104 is shifted, thepixels of overlay 110 are also shifted in unison. Accordingly, thepixels used to display the overlay 110 are not permanently fixed, andthere are several pixels used over time for displaying each point on theoverlay 110.

As an example of an orbiting pattern for the pixel array, TABLE 1 belowshows available coordinates for one particular pixel initially locatedat a23 as the shifting pattern is executed.

TABLE 1 a11 a12 a13 a14 a15 a21 a22 a23 a24 a25 a31 a32 a33 a34 a35 a41a42 a43 a44 a45From a23, an example orbiting pattern may commence according to thefollowing sequence of coordinates: a23, a24, a34, a33, a32, a22, a12,a11, a21, a31, a41, a42, a43, a44, a45, a35, a25, a15, a14, a13, andreturning to the starting position a23. The interval between each shiftmay be equal for a linear distribution. Alternatively, the interval maybe uneven according to a nonlinear distribution. The distribution mayalso alternate between linear and nonlinear.

FIG. 2 is a flow chart that shows a method 200 in accordance with anaspect of the invention. In 202, the visible display array is set as areduced size of the available horizontal pixels H and vertical pixels V.Accordingly, the visible display array may be defined as (H-n)horizontal pixels and (V-m) vertical pixels, creating n reserved pixelsin each horizontal row, and m reserved pixels in each vertical column.In 204, the input video image size is scaled to fit the defined visibledisplay array. In 205, the image is presented to the display at thereduced size to accommodate shifting of the visual display array. In206, the horizontal shift amount is set at [0, +/−N] pixels for therange (0≦|N|≦n), and a vertical shift amount is set at [0, +/−M] pixelsfor the range (0≦|M|≦m). In optional step 208, a shift frequency is set,which may be fixed within a range of one shift per 1 to 60 minutes forexample. For instance, if a shift frequency is set to one shift perhour, then a horizontal or vertical shift occurs in intervals of 60minutes. Alternatively, the range may be fixed within a range of 1 to 24hours. Alternatively, the frequency may be variable over time. In 210, aseries of horizontal and/or vertical shifts are initiated to distributethe overlay across a set of pixels to avoid a permanently fixed overlay.Each shift within the series of shifts may occur infrequently such thatit is essentially imperceptible to the camera user. The series of shiftsmay include horizontal shifts only, or vertical shifts only, or acombination of horizontal and vertical shifts. The shifting pattern maybe achieved by applying a Gaussian filter to maintain a Gaussiandistribution of the pixel array. By shifting according to a Gaussiandistribution, the line of pixels that form the overlay may have ablurred transition rather than a high contrast transition against theadjacent field of pixels over the course of time, as pixel degradationat the lines does not occur at fixed lines. Alternatively, otherdistributions may be applied to the horizontal and vertical shifts toassure that the overlay pixels are distributed over a range (0:n, 0:m).

FIG. 3 is a block diagram of an example apparatus 300, which includes adisplay 320 and an image processing system 310 configured to perform thescaling and shifting of the pixel array of method 200. The display 320may be, for example, a LCD, LED or OLED display screen resident in theimage processing system, external to the image processing system, ordistributed across multiple entities including the image processingsystem. The display 320 may be a high definition (HD) self-lit displayscreen. The image processing system 310 may be configured to perform asa multi-purpose scaler capable of scaling up or down as needed for SDand HD formats. The image processing system 310 includes a video-inprocessing unit 302 and a scaling unit 303 that may process the video insignal in an input clock domain. A video-in processing unit 302 includescircuitry and/or software modules to perform functions such as videogeneration, color control and a focus assist. A scaling unit 303 isconfigured to scale the camera video signal to a proper format in theinput clock domain. The scaling unit 303 may include an upscaling unitand/or a downscaling unit to scale the camera video signal by a scalefactor, which may be an integer or may be a fraction. The scaling unit303 may be configured to perform at least one of an upscaling ofhorizontal pixels, an upscaling of vertical pixels, a downscaling ofhorizontal pixels or a downscaling of vertical pixels. For example, ifthe video source is 3960 horizontal pixels and the display is 1980horizontal pixels, the scaling unit 303 may down scale the data samplesby ½. The scaling factor may also include the value n to account forreserved pixels in the horizontal row in regions 106, 107 as shown inFIG. 1. For example, using the previous parameters of 3960 horizontalpixels for the source and 1980 horizontal pixels for the display, afactor of [½]−n may provide a pixel array with 1980-n horizontal pixelsthat may be orbited. The scaling unit 305 may be bypassed if the scalingunit 303 can achieve the proper scaling alone.

A double data rate (DDR) clock crossing unit 304 may implemented as amemory unit (e.g., synchronous dynamic random access memory (SDRAM)) forshifting the crossing point between the input clock domain and thedisplay clock domain. The DDR clock crossing unit 304 may decouple thevideo stream between both clock domains, by buffering the video datawhen scaling unit 305 requests a sample, and maintaining a balance ofdata flow. The data transfer from the input clock domain to the panelclock domain may then occur within a valid range.

A scaling unit 305 may include an upscaling unit and/or a downscalingunit configured to scale the number of data samples for a proper formatin the display clock domain. The scaling unit 305 may be configured toperform at least one of an upscaling of horizontal pixels, an upscalingof vertical pixels, a downscaling of horizontal pixels or a downscalingof vertical pixels. For example, if the video source is 1280 horizontalpixels and the display is 1980 horizontal pixels, the scaling unit 305may upscale the data samples as appropriate. The scaling factor may alsoinclude the value n to account for reserved pixels in the horizontal rowin regions 106, 107 as shown in FIG. 1. The scaling unit 303 may bebypassed if the scaling unit 305 can achieve the proper scaling alone.

Alternatively, both scaling units 303 and 305 may work in tandem toachieve the proper display array of pixels. The scaling units 303 and305 may work alone or in combination to achieve a final scalingappropriate for the orbiting and/or a zoom function. For example,scaling units 303 and 305 may perform cross scaling such as horizontalupscale and vertical downscale, and vice-versa.

A video-out processing unit 306 includes circuitry and/or softwaremodules configured to perform functions including region of interestanalysis, text generation, wobble, waveform monitor, and/or virtual CRT(i.e., CRT behavior emulation). The video-out processing unit 306generates and sends the video out signal to the display 320.

A shift processor 307 may execute the shifting of the pixel array asdescribed above for steps 206, 208 and 210. The shift processor 307 mayset the number of pixels that the pixel array is to shift and whetherthe shift is in a horizontal direction, a vertical direction, or both.The shift processor 307 may also determine how frequently the shiftsoccur, whether constant or variable, and initiate each shiftaccordingly. The shift processor 307 may apply a Gaussian distributionto the series of shifts, which may produce an orbiting pattern about areference pixel.

A control unit 301, such as a microprocessor, may interface with thevideo-in processing unit 302, the scaling units 303, 305 the clockcrossing unit 304, the video-out processing unit 306, and the shiftprocessor 307 to control the sequence of operations and to control theinput/output flow of data. A memory 311 may be used in conjunction withthe control unit 301 for storing the information pertaining to thepixels during the scaling and shifting process, such as reduced size ofthe visual display, current array position, previous shift positions,number of pixels n or m to shift the array, and shift frequency forexample. In one embodiment, the memory 311 may store the current arrayposition prior to the display 320 being turned off. Upon restoring powerto the display 320, the memory 311 may recall the stored position of thearray, and the image on the display 320 may be presented based on thestored array position.

FIG. 4 is a conceptual diagram illustrating an example of a hardwareimplementation of the image processing system 310 within a video displayapparatus 400. In this example, video display apparatus 400 may includethe display 320, a user interface 413, and a bus architecture for thevideo input, represented generally by the bus interface 408. The businterface 408 may include any number of interconnecting buses andbridges depending on the specific application of the video displayapparatus 400 and the overall design constraints. The bus interface 408may link together various circuits including one or more processors,represented generally by processor 404, video processor 420, and imageprocessing system 310. The processor 404 may be responsible for managingthe bus 402 and general processing. The video processor 420 may includemultiple processors, such as a signal processor or other specializedprocessor. The video processor 420 may be configured to operate onpixels in the sequence of images to produce a signal representative ofone or more images present in the video input. For example, the videoprocessor 420 may perform gamma correction, color correction, sharpness,white balance, and other video processing functions. The bus interface408 may also link various other circuits such as timing sources,peripherals, voltage regulators, and power management circuits, whichare well known in the art, and therefore, will not be described anyfurther.

In one example, the display apparatus 400 may be incorporated in acamera, such that the video input is a “raw” image signal provideddirectly to video processor 420, which may process pixel information ina sequence of images to produce a standardized video outputrepresentative of a sequence of frames. In another example, the displayapparatus 400 may be a high definition display device, such as acomputer display, a television, or other display. The video inputinformation may comprise a compressed video stream and metadataincluding background information, foreground objects, motion vectors,virtual lines, object counting, object tracking and other metadata.Depending upon the nature of the apparatus 400, a user interface 413,including one or more of a keypad, speaker, microphone, or joystick, maybe provided.

FIG. 5 is a simplified block diagram illustrating an exemplary camerasystem 500 that implements the image processing system 310 in aviewfinder 504. Camera system 500 may comprise a camera 502, theviewfinder 504, and a lens system 506. Camera 502 may include an imager520, which may comprise one or more CCD or CMOS imaging devices toconvert photons to electrical video signals. Camera 502 may comprise oneor more video processors 522 that receive a sequence of images andproduce a video output having a desired frame rate, aspect ratio, etc.An encoder 524 may receive a raw video output from video processor 522and produce a formatted video signal encoded according to a particularspecification (e.g., Serial Digital Interface (SDI), H.264/MPEG-4Advanced Video Coding, or High Definition Multimedia Interface (HDMI)).The signal from encoder 524 may be output for transmission to a videoproduction system and/or over a network using transceiver 526. Encoder524 may also provide an encoded or raw video feed to viewfinder 504.

View finder 504 may include a decoder 541 which receives encoded videoor raw video from encoder 524 and provides image data for the display542. The image processing system 310 receives the video signal fromdecoder 541 and may perform the pixel array shifting process describedabove. In one example, the display 542 may include an organiclight-emitting diode (OLED) at each pixel, whereby a light-emittingdiode (LED) is coated with an emissive electroluminescent layer formedfrom an organic compound which emits light in response to an electriccurrent. These and other devices may be used to generate images on thedisplay 542.

Lens system 506 may be controlled to provide a desired opticalconfiguration of lenses, which configuration may specify, for example, adepth of field setting, a numerical aperture, and a focal length.

By way of example and without limitation, the aspects of the presentdisclosure are presented with reference to systems and methods used toconfigure various components of a video production system that may beused for production of television programming or at sports events. Thevarious concepts presented throughout this disclosure may be implementedacross a broad variety of imaging applications, including systems thatcapture and process video and/or still images, video conferencingsystems and so on.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. §112, sixth paragraph, unless the element is expressly recitedusing the phrase “means for” or, in the case of a method claim, theelement is recited using the phrase “step for.”

What is claimed is:
 1. A viewfinder apparatus, comprising: a displaycomprising an array of horizontal pixels and vertical pixels; and animage processing system configured to: present an image and an overlayon the display as a visible display array having a smaller size than thearray; and shift the visible display array by at least one pixel,wherein the presented image and overlay are shifted by the at least onepixel.
 2. The apparatus of claim 1, wherein the image processing systemfurther comprises a shift processor configured to set a maximumhorizontal shift of n pixels and a maximum vertical shift of m pixels,wherein the shift of at least one pixel comprises at least one of ahorizontal shift of N pixels in the range 1<=N<=n, or a vertical shiftof M pixels in the range 1<=M<=m.
 3. The apparatus of claim 1, whereinthe image processing system further comprises a shift processorconfigured to set a shift frequency and perform subsequent shifts of thevisible display array at intervals according to the shift frequency. 4.The apparatus of claim 3, wherein the shift processor is furtherconfigured to apply a Gaussian filter to distribute the visible displayarray.
 5. The apparatus of claim 1, wherein the image processing systemfurther comprises a scaling unit configured to scale an input videoimage size to fit the visible display array.
 6. The apparatus of claim5, wherein the scaling unit comprises at least one upscaling unit and atleast one downscaling unit configured to perform at least two of anupscaling of horizontal pixels, an upscaling of vertical pixels, adownscaling of horizontal pixels or a downscaling of vertical pixels. 7.The apparatus of claim 5, wherein the image processing system comprisesa clock crossing unit to buffer a video input signal of a first clockdomain for a scaling performed in a second clock domain.
 8. Theapparatus of claim 1, further comprising a user interface.
 9. Theapparatus of claim 1, further comprising a memory configured to store acurrent position of the shifted visible display array, wherein upondeenergizing the display and restoring power to the display, theposition is recalled from the memory, and the visible display array ispresented based on the stored position.
 10. The apparatus of claim 1,wherein the overlay comprises a center cross-mark.
 11. The apparatus ofclaim 10, wherein the center cross-mark forms a guide for a user withreference to a center of view of the display.
 12. A camera, comprising:an imager configured to convert photons to an electrical image signal;and a viewfinder comprising: a display comprising an array of horizontalpixels and vertical pixels; and an image processing system configuredto: present an image and an overlay on the display based on theelectrical image signal as a visible display array having a smaller sizethan the array; and shift the visible display array by at least onepixel, wherein the presented image and overlay are shifted by the atleast one pixel.
 13. The camera of claim 12, wherein the overlaycomprises a center cross-mark.
 14. The camera of claim 13, wherein thecenter cross-mark forms a guide for a user with reference to a center ofview of the camera.